A linear array sensor spectrometer is used to measure the irradiance of a light source at a range of wavelengths simultaneously. The slit aperture at the optical port is used to control the amount of light entering the system, which affects the collimation and thus instrument resolution. The slit is an integral part of the Czerny-Turner optical bench among others. Slits are usually fabricated using electrical discharge machining of metals, however using microelectromechanical techniques, semiconductor materials, such as silicon nitride, can also be exploited.
The optical mechanical components of a spectrometer are susceptible to misalignment due to shock and vibration as well as thermal and other physical effects, which causes the wavelengths associated with specific sensor elements to shift. In applications where the absolute wavelength or relationship between wavelengths is critical, calibration must be performed or confirmed often. In current practice, a wavelength calibration light source with a multiplicity of spectral lines is either multiplexed into the light path or, connected to the optical port of the spectrometer. Given spectral lines that cover the wavelengths of the spectrometer, a polynomial regression can be used to describe the physical relationship of the detector elements to specific wavelengths of light. Thus, a method for in situ wavelength calibration, without adding additional optical components such as a fiber or integrating sphere would be highly advantageous.